But does it have a variable explorer? Somehow this simple feature, available in MATLAB and RStudio, is sorely lacking in many Python IDEs. I put up with an unbelievable amount of crap in Spyder because I can actually inspect dataframes, matrices, etc.

It does show you the active variables (and bits of details like shapes and dtypes for numpy arrays, torch tensors, dataframes, etc): https://scripton.dev/assets/images/lib-symbols@2x.png

However, I'm assuming you want to drill down further into these (and have them displayed as a table for instance)? While the current version doesn't have that, it's definitely planned.

Vanilla vscode has some version of this in the debugging mode, you'd perhaps need to install their Python extensions but that's about it.

PyCharm does this well